Multipass boiler



April 10, 1951 Filed Sept. 27, 1946 J. H. BLAKE, JR

MULTIPASS BOILER 3 Sheets-Sheet 1 IN VENTOR Jw/A/ H. BLAKE J/E.

ATTORNEY.

April 10, 1951 J. H. BLAKE, JR

MULTIPASS BOILER 3 Sheets-Sheet 2 Filed Sept. 27, 1946 Fla. 5

FIG. 4

JOHN H. 5 AA 7 M INVENTOR.

42 3 AlTTO/ENEY.

April 10, 1951 J. H. BLAKE, JR 2,548,287

MULTIPASS BOILER Filed Sept. 27, 1946 3 Sheets-Sheet 3 JNVENTOR. Joxwv H BLAKE,J/?.

ATTORAEY Patented .Apr. 10, 1951 UNITED STATES PATENT OFFICE MULTIPASS BOILER John H. Blake, J r., Freehold, N. J.

Application September 27, 1946, Serial No. 699,759

7 Claims.

This invention relates to boilers employed for the generation of steam or hot water, and more particularly to horizontally-cylindrical, returntubular, internally-fired boilers of the type commonly designated as Scotch, and has as an object to provide an improved arrangement, disposition, and relationship of elements productive of enhanced efiiciency, extended operative life, and reduced initial and maintenance costs in boilers of such type.

A further object of the invention is to provide an improved arrangement, disposition, and interrelation of elements constituting a boiler of Scotch type applicable to and productive of increased operative eiiiciency in such boilers whether of single or multiple pass design.

A further object of the invention is to provide an improved boiler of Scotch type characterized by a novel arrangement of elements productive of more prompt and efficient thermally-induced circulation of water therein.

A further object of the invention is to provide a novel and improved arrangement of elements in a Scotch type boiler effective to obviate the characteristic disadvantages of such boilers as hitherto constructed and used.

A further object of the invention is to provide a novel and improved arrangement of elements in a Scotch type boiler whereby the structural complications inherent in multiple-pass such boilers as heretofore constructed are minimized and largely obviated.

A further object of the invention is to provide a construction and interrelation of elements constituting a Scotch type boiler readily adaptable to such variation of multiple-pass operative arrangement as may be deemed expedient or desirable in and for a given installation.

With the foregoing and other objects in view, my invention consists in the construction, arrangement, and operative combination of elements as hereinafter set forth, pointed out in my claims, and illustrated by the accompanying drawings, in which- Figure 1 is a diagrammatic section transversely through the essential elements of a conventional "Scotch boiler, the normal convection currents whereof are indicated by arrows. Figure 2 is a diagrammatic section, similar to Figure 1, illustrating a variation of element disposition primary to my invention and, by means of arrows, the convection current alteration deriving therefrom. Figure 3 is a longitudinal, substantially axial section through a typical two-pass boilerincorporating the modifications typified by Fig-' ure 2 and taken on line 3--3 thereof. Figure 4 is a view similar to Figure 3 taken on line 4-4 of Fig. 5 and illustrating adaptation of the principles of the invention to the development of a three-pass boiler. Figure 5 is a cross section taken on the indicated line 55 of Figure 4. Figure 6 is a cross section taken on the indicated line 6-6 of Figure 4. Figure 7 is a View similar to Figure 3 taken on the line of Fig. 8 and illustrating typical extension of the principles of the invention to the development of a fourpass boiler. Figure 8 is a cross section taken on the indicated line 8-8 of Figure '7. Figure 9 is a cross section taken on the indicated line 9-9 of Figure '7.

Horizontally-cylindrical, internally-fired,- return-tubular boilers, in a multitude of specific constructions and arrangements, are extensively in use because of certain of their well known attributes and characteristics and in spite of certain equally well known structural and operative deficiencies. Such boilers conventionally consist of a cylindrical shell disposed with its axis horizontal, a furnace or fire box longitudinally traversing the shell with its axis in the vertical axial plane of the shell, one or more heads spaced inwardly from an adjacent shell end and traversing the shell in perpendicular relation with the axis thereof to provide corresponding chambers and, where two such heads are employed, fire tubes connecting between .and opening through said heads longitudinally of the boiler. In the operation of such boilers, the interior of the shell between the heads and about the tubes is charged with water to a depth sufficient to at all times cover the tubes and furnace, and combustion is developed in the firing end of the furnace so that the heat therefrom may longitudinally traverse the furnace, heating the latter and the water thereabout, and be passed and repassed through the fire tubes from one and to .the other, of the shell end chambers until the effective heat of combustion has been largely lost to the boiler water and the cooled smoke and gases are vented from the final end chamber to atmosphere; the

circulation and direction of the combustion products from the furnace and through the tubes be-' ing controlled by conventionally-horizontal baffles sub-dividing the shell end chambers. defect in the operation of such boilers when arranged with the furnace axis in the vertical axial plane of the shell, as has been the apparently universal practice heretofore, is exemplified by the diagram of Figure 1. With the furnace 'll disposed approximately centrally of the shell Hi, the

A prime.

altitudinal variation of said furnace away from the shell center being of no material significance, convection currents in the water surrounding the furnace and deriving from the products of combustion traversing the latter take the paths outwardly and upwardly from the furnace exterior indicated typically by the arrows of the view, certain of said convection currents impinging against the cylindrical walls of the shell in and being thereby deflected downwardly for a space and then promptly ascending in conformity with the known properties of thermal currents in a singlepass boiler of this type, which characteristic convection currents are productive of a marked temperature differential between the upper and lower portions of the boiler water, and the portion of the water below the furnace and in the bottom of the shell is very slow to heat, marks a cold spot characteristic of Scotch type boilers, and is productive of undesirable strain, resulting from unequal thermal expansion, on the boiler shell and related structures. In multiple-pass Scotch boilers of conventional design, horizontally-disposed baffles traversing the shell end chambers are employed to direct the products of combustion from the furnace l I, first through the tubes traversing the boiler lower portion and then progressively through the higher tube banks, but even this arrangement does not eliminate the characteristic cold spot directly beneath the furnace, since the convection currents deriving from the heated tubes ascend and circulate away from the boiler bottom, and the horizontal bafiles introduce structural and maintenance problems of considerable importance.

The typical cylindrical form and axially parallel relation of the shell and furnace elements characteristic of Scotch boilers, together with the known and consistent behavior of thermal currents in the water body charged within such shell, conduce to a simple and effective arrangement through which the cold spot may be operatively eliminated for more rapid and uniform heating of the boiler water; which arrangement has further advantage in that it permits of multiple pass development through the agency of vertical, rather than horizontal, baiiies of relatively much more economical construction and maintenance. The improved arrangement 'primary to the instant invention is typified by Figure 2 and involves simply a shift of the furnace ll laterally toward one side or the other of the shell so that the furnace axis, while maintained parallel with the shell axis, lies without the vertical axial plane of the shell, regardless of the altitudinal relative disposition of the furnace. The precise relation between the furnace I l and the shell In in the improved arranga ment will naturally vary somewhat in particular boiler constructions, the altitudinal disposition of the furnace within the shell and the spacing between the more nearly adjacent shell and furnace Walls being details of specific design for determination in accordance with the structural and operative factors encountered in the particular instance. Regardless of the exact location of the furnace ll within its shell l0, lateral shifting of said furnace to an eccentric, longitudinallyparallel relation with the shell results in a convection current circulation of the general order of that represented by the arrows in Figure 2, it

being obvious that the rising currents generated between the more nearly adjacent furnace and shell walls tend to orbitally traverse the entire water body in generally circular path determined by the shell outline and induce a circulation through and an upward travel of water away from the typical cold spot of conventional such boilers to effect a much more uniform and rapid heating of the entire boiler water charge.

In a single-pass boiler incorporating the improved arrangement, no fire tubes are employed and the products of combustion pass from the furnace l l to an end chamber or stack at the boiler end remote from the firing end of the furnace, the heating effect had on the boiler water charge deriving entirely from the heat radiated by the furnace walls and the convection currents thereby developed. Such single-pass boilers are of low efliciency and little employed, hence a specific illustration thereof is not included in the drawings, but it is readily apparent that the improved arrangement is of marked advantage in stimulating the water circulation within, eliminating the cold spot from, and enhancing the efficiency of even single-pass boilers.

In multiple-pass boilers of the general type under consideration, a head l2 interiorly and perpendicularly traverses the shell H1 in inwardly-spaced relation with each of the shell end closures to form a chamber at each end of the boiler, the furnace II traverses the end chamber at the furnace firing end in insulated, non-communicating relation therewith and opens through the head l2 remote from its firing end for discharge of products of combustion into the chamber at the rearward end of the boiler, and fire tubes I3, spaced apart in axial parallelism with the shell and furnace, open through and communicate between the heads [2 to provide passage for the products of combustion from one and to the other of the end chambers. For a boiler of two-pass type, no baffles need be employed in either of the end chambers, such a construction, represented by Figure 3, requiring only that a vent pipe or a stack l4 communicate with the chamber at the firing end of the boiler so that the products of combustion delivered fromthe furnace H to the rearward end chamber of the boiler are induced to return forwardly of the boiler through the tubes I3, into the forward end chamber, and thence through the stack #4 to atmosphere; the only variation from conventional design and construction represented by the iiii proved arrangement when applied to either single or two pass constructions being the shifting of the furnace H laterally away from the vertical axial plane of the shell.

The structural advantages of the improved arrangement became particularly significant in three, four, and higher, pass boilers extensively employed because of their relatively higher elliciency, wherein bafiles traverse and divide the end chambers for the direction of products of combustion successively through banks of the tubes [3 from one and to the other of the boiler end chambers. adaptation of the improved arrangement to function as a three-pass boiler. In the three-pass arrangement, the stack l4 serves the end chamber remote from the furnace firing end and a single bafile 15, of any suitable material and specific construction, vertically traverses the end chamber at the rearward end of the boiler between the furnace II and stack l4 and closes at its ends against upper and lower arcs of the shell H3 and at its sides against the adjacent head [2 and boiler end closure to sub-divide its chamber into two;compartments into whichap proximately equal effective areas of the tubes 13 Figures 4, 5, and 6 typify an.

open. With the illustrated construction, products of combustion pass from the furnace H to the stack M as indicated by the arrows in Figure 4, giving up their heat to the boiler water charge as they are-caused to three times longitudinally traverse the boiler between the heads l2. The baflle l5 may be of any material and specific construction suited to its function of dividing and obstructing a boiler end chamber in exposure to hot products of combustion, it being common practice to line the boiler end chambers with and to fabricate boiler bafiies from, refractory material, or to form such bafiles from metal coated or covered with refractory material. Due to its vertical disposition made possible by use of the improved furnace arrangement, the baffle [5 may be relatively quite light in weight, inexpensive of production, and conveniently and 'securely anchored to the associated boiler elements in a manner that insures long operative life with a minimum of maintenance and with little failure potential, the absence of any unsupported horizontally-disposed weight in the baflle l5- obviating the necessity for ponderous and difficult construction of the type heretofore used and largely eliminating failures due to warping and buckling of the heat-exposed bafiie surfaces.

An extension of the principles of the invention to the development of a four-pass boiler is represented by Figures 7, 8, and 9, wherein the only difference over the showing of the preceding three figures is the provision of baffle 15 in vertically-traversing, sub-dividing relation with the boiler forward end chamber, connection of the stack I4 with and to serve said forward end chamber, and a shift in the position of the baflie I5 of the boiler rear end chamber to balance the tube effective area on one side thereof with the combined tube and furnace effective areas on its other side; the baffie in the forward end chamber being so disposed as to approximately divide the effective area of the tubes opening to the side of the rear end chamber baffle l5 remote from the furnace; which disposition of baffles and stack results in repetitious flow of the products of combustion through the boiler water charge by means of the tubes I3 in the manner and direction indicated by the arrows of Figure '7, and hence in a four-phase exposure of the heat inherent in said production products to and for heating effect on said boiler charge.

Obviously, through the provision of suitablydisposed baflies in the boiler end chambers, the novel principles of the invention may be applied to the development of multiple-pass boilers wherein the products of combustion may be passed and repassed through the boiler water charge any desired number of times, location of the furnace adjacent a shell side wall insuring such circulation of the boiler water charge as will prevent development of the hitherto characteristic cold spot and permitting vertical disposition of the end chamber baffles, in such number and spacing as may be appropriate to a given boiler design, and consequent complete avoidance of the structural and operative disadvantages of the horizontally-disposed baflles previously employed.

Since many changes, variations, and modifications in the specific form, construction, and arrangement of the elements shown and described may be had without departing from the spirit of my invention, I wish to be understood as being limited solely by the scope of the appended claims, rather than by any details of the illustrative showing and foregoing description.

I claim as my invention 1. A boiler comprising an axially-horizontal, cylindrical shell chargeable with water, chambers at and coextensive with the ends of said shell, a furnace traversing one of said chambers and said shell for discharge into the other of said chambers in axially-parallel, laterallyoffset relation with the shell axis, fire tubes traversing said shell in parallel With said furnace and connecting with said chambers, an outlet stack serving one of said chambers, and vertically extending means obstructing at least that one of said chambers served by said stack 1ongitudinally of said shell and chordally thereof in end-closing relation with the associated chamber walls between the thus formed adjacent tube groups for direction of gas flow from said furnace through successive groups of said tubes and to said stack.

2. A boiler comprising an axially-horizontal,

cylindrical shell chargeable with water, chambers at and coextensive with the ends of said shell, a furnace traversing one of said chambers and said shell for discharge into the other of said chambers in axially-parallel, laterally-offset relation with the shell axis, fire tubes traversing said shell in parallel with said furnace and connecting with said chambers, an outet stack serving the chamber at the furnace discharge end, and a baffle extending vertically and obstructing said latter chamber longitudinally of said shell and chordally thereof in end-closing relation with the associated chamber walls between the furnace discharge end and the stack, and also between the thus formed adjacent tube groups for the direction of gas flow from said furnace successively through the separated tube groups and to said stack.

3. A boiler comprising an axially-horizontal cylindrical shell chargeable With water, chambers at and coextensive with the ends of said shell, a furnace traversing one of said chambers and said shell for discharge into the other of said chambers in axially-parallel, laterally-offset relation with the shell axis, fire tubes traversing said shell in parallel with said furnace and connecting with said chambers, an outlet stack serving the chamber traversed by said furnace,

and parallel baflies, one in each chamber, extending vertically and obstructing said chambers longitudinally of said shell and chordally thereof in end-closing relation with the associated chamber walls between the thus formed adjacent tube groups and said baffies being at different distances from said furnace for direction of gas flow from the latter successively through the so separated tube groups and to said stack.

4. In a boiler having an axially-horizontal, cylindrical shell chargeable with water, chambers at and coextensive with the ends of said shell, an outlet stack serving one of said chambers, and fire tubes longitudinally traversing said shell connecting with said chambers, the combination with a furnace traversing one of said chambers and said shell for discharge into the other of said chambers in axially-parallel, laterally-offset relation with the shell axis, of baffles spaced from and paralleling the furnace axis, said baflies ex-, tending vertically in obstructing relation within said chambers and chordally thereof in endclosing relation with the associated chamber walls between the thus formed adjacent tube groups for the direction of gas flow from said furnace successively through the so-separated tube groups.

5. In a boiler having an axially-horizontal, cylindrical shell chargeable with water, chambers at and coextensive with the ends of said shell, an outlet stack serving one of said chambers, and fire tubes longitudinally traversing said shell connecting with said chambers, a furnace traversing the chamber remote from said stack and said shell for discharge into the stack-served chamber in axially-parallel, laterally-offset relation with the shell axis, and a baflle spaced from and paralleling the furnace axis, said bafiie extending vertically in obstructing relation within the stack-served chamber and chordally thereof in end-closing relation with the associated chamber Walls between the thus formed adjacent tube groups for the direction of gas flow from said furnace successively through the so-separated tube groups and to said stack.

6. In a boiler having an axially-horizontal, cylindrical shell chargeable with water, chambers at and coextensive With the ends of said shell, an outlet stack serving one of said chambers, and fire tubes longitudinally traversing said shell connecting with said chambers, a furnace traversing the chamber served by said stack and said shell for discharge into the chamber remote from said stack in axially-parallel, laterally-offset relation with the shell axis, and a vertical baflle spaced from and paralleling the furnace axis in obstructing relation within each of said chambers on the same side of said furnace and chordally 8 of said shell in end-closing relation with the associated chamber walls between the difierent thus formed adjacent tube groups for the direction of gas flow from said furnace successively through the so-separated tube groups and to said stack.

7. In an internally-fired, return-tubular, multip-le-pass, Scotch-type boiler, a furnace paralleling and offset laterally from the boiler axis, and a vertical bafiie at each boiler end on the same side of and differently spaced from said furnace chordally of the associated boiler end in separating relation between the thus formed adjacent boiler tube groups for the direction of gas flow sequentially through the boiler.

JOHN H. BLAKE, JR.

REFERENCES orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 236,011 Elward Dec. 28, 1880 1,151,127 Schroder Aug. 24, 1915 1,605,100 Dineen Nov. 12, 1926 1,751,533 Taylor Mar. 25, 1930 1537,53 1 Conklin Dec. 22, 1931 1,934,621 Wafter Nov. 7, 1933 1,940,973 Sharp Dec. 26, 1933 1,950,756 Sharp Mar. 13, 1934 2,034,452 Does de Bije U Mar. 17, 1936 2,055,949 Scharp Sept. 29, 1936 

